We've seen recent pictures of broken axles, but they had been welded; never seen an original axle broken.

I had an accident where the front axle was pushed over 6 inches back one side so the wishbone was badly bent. The car sat a week or two with the axle twisted back. Once released from the wishbone it popped back into shape and careful checking showed it had gone straight back into its original position; only the wishbone needed work.

The picture illustrates how ductile the vanadium steel was and it should show the strength of the material. However - as the members of the two-part crank club have experienced the hard way - there are many other parameters than just ductility. Resistance to metal fatigue for example. Metallurgy have evolved a great deal since and we understand better what happens on the molecular level thanks to electron microscopes. Ford did indeed pioneered the use of metallurgy in automotive design, but they just haven't revealed all the secrets.